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Fixed support for boost variant. #768

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Fixed support for boost variant. #768

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74 changes: 64 additions & 10 deletions include/cereal/types/boost_variant.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
\ingroup OtherTypes */
/*
Copyright (c) 2014, Randolph Voorhies, Shane Grant
Copyright (c) 2022, Nokia
All rights reserved.

Redistribution and use in source and binary forms, with or without
Expand Down Expand Up @@ -38,8 +39,11 @@
#endif

#include "cereal/cereal.hpp"
#include <boost/variant/variant_fwd.hpp>
#include <boost/mpl/at.hpp>
#include <boost/mpl/size.hpp>
#include <boost/mpl/size_t.hpp>
#include <boost/variant/static_visitor.hpp>
#include <boost/variant/variant_fwd.hpp>

namespace cereal
{
Expand Down Expand Up @@ -130,6 +134,62 @@ namespace cereal
load_variant_impl( ar, variant, typename std::is_default_constructible<T>::type() );
}
};

//! @internal
template<size_t ... indices>
struct sequence
{
};

//! @internal
template<typename S1, std::size_t x>
struct push_back;

//! @internal
template<std::size_t ... indices, std::size_t x>
struct push_back<sequence<indices...>, x>
{
using type = sequence<indices..., x>;
};

//! @internal
template<std::size_t N>
struct make_sequence;

//! @internal
template<>
struct make_sequence<0>
{
using type = sequence<>;
};

//! @internal
template<std::size_t N>
struct make_sequence
{
using type = typename push_back<typename make_sequence<N - 1>::type, N - 1>::type;
};

//! @internal
template <class Archive, typename ... VariantTypes, size_t ... indices> inline
void load_variant_with_sequence( Archive & ar, boost::variant<VariantTypes...> & variant, sequence<indices...>)
{
int32_t which;
ar( CEREAL_NVP_("which", which) );

using TypesSequence = typename boost::variant<VariantTypes...>::types;
using LoadFuncType = void(*)(Archive &, boost::variant<VariantTypes...> &);
CEREAL_CONSTEXPR_LAMBDA LoadFuncType loadFuncArray[] = {
&boost_variant_detail::load_variant_wrapper<typename boost::mpl::at<
TypesSequence,
boost::mpl::size_t<indices>>::type>::load_variant...};

if(which >= int32_t(sizeof(loadFuncArray)/sizeof(loadFuncArray[0])))
throw Exception("Invalid 'which' selector when deserializing boost::variant");

loadFuncArray[which](ar, variant);
}

} // namespace boost_variant_detail

//! Saving for boost::variant
Expand All @@ -146,16 +206,10 @@ namespace cereal
template <class Archive, typename ... VariantTypes> inline
void CEREAL_LOAD_FUNCTION_NAME( Archive & ar, boost::variant<VariantTypes...> & variant )
{
int32_t which;
ar( CEREAL_NVP_("which", which) );

using LoadFuncType = void(*)(Archive &, boost::variant<VariantTypes...> &);
CEREAL_CONSTEXPR_LAMBDA LoadFuncType loadFuncArray[] = {&boost_variant_detail::load_variant_wrapper<VariantTypes>::load_variant...};

if(which >= int32_t(sizeof(loadFuncArray)/sizeof(loadFuncArray[0])))
throw Exception("Invalid 'which' selector when deserializing boost::variant");
using TypesSequence = typename boost::variant<VariantTypes...>::types;
using IndexSequence = typename boost_variant_detail::make_sequence<boost::mpl::size<TypesSequence>::value>::type;

loadFuncArray[which](ar, variant);
load_variant_with_sequence(ar, variant, IndexSequence());
}
} // namespace cereal

Expand Down
20 changes: 16 additions & 4 deletions unittests/boost/boost_variant.hpp
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
/*
Copyright (c) 2015, Kyle Fleming
Copyright (c) 2022, Nokia
All rights reserved.

Redistribution and use in source and binary forms, with or without
Expand Down Expand Up @@ -29,6 +30,7 @@

#include "../common.hpp"
#include <cereal/types/boost_variant.hpp>
#include <boost/mpl/vector/vector30.hpp>
#include <boost/variant.hpp>

struct NonDefaultConstructible
Expand Down Expand Up @@ -58,14 +60,12 @@ template <> struct LoadAndConstruct<NonDefaultConstructible>
};
} // end namespace cereal

template <class IArchive, class OArchive> inline
void test_boost_variant()
template <class IArchive, class OArchive, typename VariantType> inline
void test_boost_variant_case()
{
std::random_device rd;
std::mt19937 gen(rd());

using VariantType = boost::variant<int, double, std::string, NonDefaultConstructible>;

VariantType o_bv1 = random_value<int>(gen);
VariantType o_bv2 = random_value<double>(gen);
VariantType o_bv3 = random_basic_string<char>(gen);
Expand Down Expand Up @@ -102,4 +102,16 @@ void test_boost_variant()
CHECK_EQ( boost::get<NonDefaultConstructible>(i_bv4).index, boost::get<NonDefaultConstructible>(o_bv4).index );
}

template <class IArchive, class OArchive> inline
void test_boost_variant()
{
using VariantType = boost::variant<int, double, std::string, NonDefaultConstructible>;

using TypeList = boost::mpl::vector4<int, double, std::string, NonDefaultConstructible>;
using OversizedVariantType = boost::make_variant_over<TypeList>::type;

test_boost_variant_case<IArchive, OArchive, VariantType>();
test_boost_variant_case<IArchive, OArchive, OversizedVariantType>();
}

#endif // CEREAL_TEST_BOOST_VARIANT_H_